It is known to operate fuel cell systems, particularly proton exchange membrane fuel cells, utilizing substantially pure hydrogen, frequently referred to as “industrial grade” hydrogen. Hydrogen in liquid form is retained in a cryogenic tank, which can reduce the amount of heat absorbed from the environment and therefore reduce the boiling of the hydrogen (which has a boiling point of 20° K, −253° C., 423° F.). When utilized in a fuel cell system, gas is tapped from the top of the cryogenic tank and fed, typically through a control valve, to the anodes of the fuel cell. When there is and will be no demand for power from the fuel cell power plant, it is typically shut down; during this period, the liquid hydrogen boils to some extent and the boil-off hydrogen gas is conventionally purged to ambient. This reduces system efficiency (by loss of fuel) and creates a safety issue.
PEM fuel cells which operate with substantially pure hydrogen typically employ a fuel recycle loop which may include a blower between the anode exit and the anode inlet of the fuel cell stack; the recycle both improves overall fuel utilization and avoids localized fuel starvation. If a blower is used in the recycle loop, condensation can occur in the blower when the system is not operating during cold weather. This may result in ice formation which interferes with blower operation.
Operation of the fuel cell power plant at near-zero current density to consume boil-off hydrogen, during periods of nominal shut down, allows the fuel cell voltage to become very high, which leads to deterioration of the cells and degradation of performance.